1. Field of the Invention
The present invention relates to an audio apparatus, a controller, an audio system, and a method of controlling an audio apparatus, and in particular, to a technique to expand functions of the audio apparatus.
2. Description of the Related Art
FIG. 11 shows a block diagram of an outline of an amplifier system as an example of a stand-alone audio system of the prior art.
An external compact disk (CD) player supplies a digital audio signal or an analog audio signal to a CD player terminal T1. An external tuner inputs an analog audio signal to a tuner terminal T2. Other audio signals are fed to a first auxiliary terminal T3 and a second auxiliary terminal T4. An input selector SL is connected to the terminals T1 to T4. The selector SL includes a digital-to-analog (D/A) converter and an analog-to-digital (A/D) converter, which are not shown. An analog audio signal is delivered via the selector SL to an audio amplifier section AM. The amplifier section AM includes a digital signal processor (DSP) to execute sound field processing through digital signal processing and amplifies the audio signal, and then outputs the amplified signal to a speaker terminal Ts. The terminal Ts is connected to a loudspeaker, not shown. A central processing unit (CPU) 150 controls the overall operation of the amplifier system AS. A read-only memory (ROM) 151 stores various programs for DSP, data for DSP which are used for executing sound field processing, various control programs, and control data which are used by CPU 150. A random access memory (RAM) 152 serves as a work area to temporarily store various data items. A display section 153 displays various information items such as a sound source being selected and a DSP mode. An operator panel 154 includes various types of operation keys.
A bus 155 connects the input selector SL, the CPU 150, the ROM 151, the RAM 152, the display 153, and the operator panel 154 to each other.
Operation of the amplifier system will be briefly described.
First, description will be given of a situation in which DSP is not conducted. When a user activates a selection switch, not shown, of the operator panel 154, an operation state of the panel 154 is notified via the bus 155 to the CPU 150. The input selector SL connects under control of the CPU 150 one of the terminals T1 to T4 to the audio amplifier section AM.
An external equipment inputs an analog audio signal via the selector SL to the amplifier section AM. The amplifier section AM amplifies the input signal and then outputs the amplified signal to the speaker terminal Ts. The speaker connected to the terminal Ts sounds.
Concurrently, the display section 153 displays information of the selected sound source (e.g., a CD player) or the like.
Next, description will be given of a situation to conduct DSP. When a user operates a selection switch and a DSP mode selection switch, not shown, of the panel 154, an operation state of the panel 154 is notified via the bus 155 to the CPU 150. Under control of the CPU 150, the input selector SL sequentially stores a digital signal obtained by A/D converting an analog audio signal inputted from one of the terminals T1 to T4 in an RAM in the DSP in the amplifier section AM.
Under control of the CPU 150, the DSP reads from the ROM 151 a program corresponding to the selected DSP mode (“HALL”, “JAZZ”, “ROCK”, or “DISCO” mode) and conducts DSP for the digital audio signal stored in the DSP RAM. The amplifier section AM amplifies the analog audio signal resultant from the DSP and then outputs the amplified signal to the speaker terminal Ts. The speaker connected to the terminal Ts produces sound.
The display section 153 displays information of the selected sound source (e.g., a CD player), the selected DSP mode (e.g., “JAZZ”), and the like.
Description will now be given of operation in which a 4-speaker playback is achieved by an audio amplifier connected to two speakers. A sound field processor SFP is used to produce playback sound of virtual rear speakers.
Assume that a front side of a listener has an azimuth of 0°. As shown in FIG. 12, the ROM 160 beforehand stores virtual three-dimensional DSP parameters for virtual speakers arranged with an azimuth of 120° in the rear side of the listener.
Data items of the DSP parameters are prepared to cope with respective sampling frequencies of a source signal, namely, 48 kHz, 44.1 kHz, and 32 kHz. In the processing of the DSP, the system uses DSP parameters corresponding to a sampling frequency of a sound source selected by the user.
In the amplifier of the prior art as above, the DSP parameter data (control data) is beforehand stored in the ROM. Therefore, the system cannot easily satisfy various requirements of the user, neither the user can simply modify the DSP parameter data.
The DSP control program is also stored in the ROM in advance. Even a function which can be added to the audio amplifier in consideration of the system configuration cannot be easily added thereto in the prior art.
This leads to a problem, namely, the user must buy another system to implement a new function.